It is often necessary to measure pressure across a relatively large pressure range with a high degree of accuracy, where the accuracy is typically specified as a percent of full scale. A pressure transducer can be manufactured to have a high accuracy tolerance at full scale, but it can be relatively inaccurate when the measured pressure range is a small fraction of the full scale. To partly address this issue, sensors can be made with multiple transducers, each of which is optimized for a specific portion of the pressure range. For example, it may be necessary to measure a 10 PSI pressure to within 0.05 PSI at one time and then later measure a 500 PSI pressure to within 0.25 PSI at the same location. Certain conventional sensor systems may require two different sensors and associated circuitry to make these measurements. However, such a measurement could be made with a multi-transducer sensor package, provided that the 10 PSI sensor that could withstand the 500 PSI pressure. Within the past several years it has become possible to use a single, high-pressure sensor to more accurately measure a lower pressure using a variety of signal processing techniques. The use of programmable gain amplifiers, digital thermal correction, and high accuracy analog to digital converters has enabled accuracies approaching 0.05% over a number of different pressure ranges. For example, the same 500 PSI sensor could be used to measure ranges such as 0-10 PSI, 0-50 PSI, 0-100 PSI, and 0-500 PSI.
These techniques work well and can be used for many applications; however, sensor noise can limit the use of the lower range of the sensor. Sensor noise level is influenced by many things, but in most instances the dominant source is thermal noise. For a typical piezoresistive sensor, thermal noise at a 10 kHz bandwidth is 0.005%. This can be lowered by reducing the bandwidth; however, in order to be a useful sensor, some bandwidth is needed and not all noise sources are bandwidth dependent. The lower floor of noise level is approximately 0.001% which means that a sensor can usefully be re-ranged to no more than about one tenth its full-scale range. A need still exists for sensor systems and methods that can measure a wide pressure range with high accuracy.